The invention relates to an apparatus for particulate solids regeneration which comprises a regenerator housing containing fluidization means arranged below spent solids inlet means and regenerated solids outlet means having fluid in- and outlet means, and further comprising at least one external heat exchanger housing containing heat exchanger means and communicating with the regenerator housing via solids in- and outlet means.
Such apparatus is known and has the advantage that relatively high rates for deposit (e.g. coke) burn-off for the spent solids can be attained in the regenerator without excessive temperature increases as a result of the cooling of the hot solids taking place in the heat exchanger housing. Therefore, such a known apparatus is particularly suited for continuously regenerating Fluid Catalytic Cracking (FCC) catalyst particles.
However, the known apparatus has as a disadvantage that the temperature inside the regenerator, in particular in the section thereof directly above the fluidization means where hot regenerated solids are withdrawn (through the regenerated solids outlet means), is in some cases difficult to control, in particular when a FCC regenerator is to be operated in complete CO combustion mode i.e. substantially completely converting carbon monoxide produced during coke burn-off into carbon dioxide with a relatively large combustion air/solids ratio.
Moreover, known apparatus generally comprise rather complicated riser systems and flow regulation means (including valves) to transport regenerated solids back from the heat exchanger to the regenerator.
Surprisingly, it has now been found that the aforementioned disadvantages can be overcome by an apparatus as described hereinbefore in which at least one solids outlet means directly connect the lower part of the heat exchanger housing(s) with a section of the regenerator housing above the fluidization means.